Batteries are electrochemical devices that are employed in various systems to provide electric energy from chemical reactions occurring in cells and are preferably rechargeable. Batteries are employed in various systems, including, e.g., ground vehicles. Known battery technologies include lithium iron phosphate (LiFePO4) cells and other technologies that exhibit a flat voltage response during charge/discharge events. A flat voltage response during charge/discharge events makes predicting a state of charge (SOC) difficult except at the end points near the top and bottom of charge. Known systems for monitoring SOC use coulomb counting and rely on the end points to reset the SOC. Battery charging and discharging can cause phase transitions in the active materials that correlate to intercalation and de-intercalation as the battery discharges and charges.
Known vehicle systems include powertrain systems that provide tractive torque for propulsion, with some of the tractive effort originating from a battery. Such powertrain systems may include hybrid systems, all-electric systems, and extended-range electric systems that can be configured to operate in various operating modes to generate and transfer torque to a driveline.